Memory is one type of integrated circuitry, and is used in electronic systems for storing data. Integrated memory is usually fabricated in one or more arrays of individual memory cells. The memory cells are configured to retain or store memory in at least two different selectable states. In a binary system, the states are considered as either a “0” or a “1”. In other systems, at least some individual memory cells may be configured to store more than two levels or states of information.
An example type of memory is dynamic random access memory (DRAM). A DRAM unit cell may comprise a transistor in combination with a capacitor. The capacitor may be considered to be a data storage device in that the charge state of the capacitor corresponds to a memory state of the memory cell.
Some memory comprises unit cells having programmable material between a pair of electrodes. The programmable material has two or more selectable resistive states to enable storing of information, and thus the memory unit cells are data storage devices. Examples of such memory cells are resistive RAM (RRAM) cells, phase change RAM (PCRAM) cells, and programmable metallization cells (PMCs)—which may be alternatively referred to as a conductive bridging RAM (CBRAM) cells, nanobridge memory cells, or electrolyte memory cells. The memory cell types are not mutually exclusive. For example, RRAM may be considered to encompass PCRAM and PMCs.
The unit cells comprising programmable material may be leaky, and accordingly select devices (i.e., access devices) may be provided to improve the control of current to and from the unit cells. The select devices may be any of numerous devices, including, for example, diodes, switches, field effect transistors, bipolar junction transistors (BJTs), etc.
Difficulties may be encountered in the fabrication of integrated circuitry, such as memory. Accordingly, it is desired to develop new methods of forming integrated circuitry.